 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| . |  |
. |
 by Staff Writers Washington DC (SPX) Oct 04, 2018
When 17 years ago astronomers for the first time pointed a 1000 frames per second camera to the sky to look at meteors, known as shooting stars, they detected a surprising new phenomenon. The bright meteor of a few meters in size was engulfed in a glowing halo of hundreds of meters in size. There has been no convincing explanation for this halo, until now/ A new study by a team of scientists has revealed that the meteor halo might share similarities to the aurora glow. This opens up an entirely new avenue in the exploration of meteors and their interaction with the Earth's atmosphere. Their study is published in Monthly Notices of the Royal Astronomical Society and it describes a two-step process that leads to the appearance of this glow. The story begins at about 120 km altitude, where a fast-flying space rock starts to experience intense evaporation due to its collision with the Earth's atmosphere. Individual collisions between the evaporated atoms and the atmospheric molecules are so intense that molecules break apart into atoms, and atoms start to lose their electrons. This hot mixture of molecules, atoms, electrons and ions (atoms that lost one or more electrons) is known as a meteor plasma and it is the main source of light that we recognize in the sky as a shooting star. In this new study authors added the Earth magnetic field into this mix and realized that under certain conditions the magnetic field will slow down the flight of electrons, leaving the meteor with an excess of positive ions. When the meteor reaches about 105 km altitude, this charge separation can lead to a strong local electric field around the positively charged meteor. At this point the second step kicks in. The meteor plasma also contains some protons, which are just hydrogen atoms that lost their electron. Unlike other positive ions, protons are light enough to be push out of the meteor by the local electric field. The protons quickly accelerate and then slam into the surrounding atmosphere. It actually takes lots of collisions with the atmospheric molecules and quite some distance to completely slow down such an ejected proton. Because of these collisions, the atmospheric molecules get excited and then release light, which we see as a glow around the meteor. Interestingly enough, the light from so called proton auroras is produced in the same way, except that there very fast protons come from the outer space. "The entire mechanism breaks down at altitudes below about 100 km", says Dejan Vinkovic, the leader of the team. "Ions and electrons want to stay close together, but their motion out of this equilibrium is driven by two processes - one is collisions they experience with other particles, and the other is the magnetic force that makes them move in a tiny circle. "If the altitude is too low, the gas densities are high enough for collisions to dominate and break up the grip that the magnetic field has on electrons. If the altitude is too high, both ions and electrons are affected by the magnetic field and, again, there is no charge separation", explains Vinkovic. In addition to the numerical simulation of this entire process, the authors also show how the charge separation could be behind some other still unexplained phenomena that accompany the flight of shooting stars. This opens an avenue for more theoretical and numerical work, combined with the new generation of advanced observational techniques, on the still not fully understood phenomenon of shooting stars. The other authors include Ante Siljic, Frane Lunic and Jurica Teklic. Although they started this research while they were still at the University of Split, Croatia, now they work for other public and private organizations. Vinkovic is now also the director of Science and Society Synergy Institute in Croatia.
Meteorite hunting with Marc Fries Pasadena CA (JPL) Sep 21, 2018 Thousands of meteorites fall onto the Earth each year. When a fall occurs in an accessible area, scientists and amateur space enthusiasts pursue the specimens, often submitting them to collections that serve planetary research. The Astromaterials Research and Exploration Science (ARES) division at NASA's Johnson Space Center studies meteorites and is implementing tools and technique to more easily recover meteorites. We sat down with Dr. Marc Fries of ARES to learn more about meteorites and why th ... read more
|
|||||||||||||
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |
del.icio.us
Digg
Reddit
Google
